Japanese Patent Application Publication No. 2007-317779 discloses an exemplary trench gate type semiconductor device. The semiconductor device includes an n-type drift region and a p-type body region disposed on a front surface side of the drift region. In this semiconductor device, a gate trench penetrating the body region and extending to the drift region is formed. A gate electrode is disposed within the gate trench and opposes the body region with an insulator interposed therebetween. A p-type diffusion region is formed in a region surrounding a bottom portion of the gate trench.